Wireless communication may require the use of radio connections, and in case one of the communication endpoints is mobile, such as a mobile telephone, wireless communication is conducted using battery power. As mobile wireless communication devices, such as cellphones, laptop computers, tablet computers, personal digital assistants and the like, become more complex they tend to draw on more battery power. For example, a large colour display consumes more power than a smaller monochrome display. Likewise a faster data connection, or a data connection that is continuously open, consumes more power than a slower connection, or one that is only intermittently open.
Continuously connected services, for example email, chat, notification and presence services, may preferably have access to a connection that is always open. An open connection in this context refers to a connection that needn't be separately established using a connection or bearer establishment procedure, for each data unit sent over the connection. Thus an application running on a tablet computer, for example, may request a connection that remains open for several hours at a time.
Maintaining a connection in an open state in wireless communication may require that data is exchanged between the wireless communication endpoints, for example at periodic intervals, to ensure that both endpoints are still participating in the connection and that receivers are able to follow changes in a radio channel between the communication endpoints. For example, in cellular communications the base station and mobile terminal may need to maintain power control and channel estimation in order to keep a radio bearer interconnecting them in an active mode. Information exchanged to maintain a connection in an open state may be referred to as control information.
Transmitting control information to maintain a connection in an open state involves drawbacks. For example, transmitting control information from a mobile terminal consumes battery power, and transmitting control information from a base station consumes energy. A base station may have access to a stable power supply, but energy may still be subject to charge. Exchanging control information over an air interface between a mobile terminal and a base station consumes air interface resources. In code division multiple access, CDMA, schemes, the exchange of control information also raises the interference level in the cell, causing all mobile terminals attached to the cell to increase their transmit power. This in turn increases battery drain in said all mobile terminals.